Lymphatic System and Lymphoid Organs and Tissues

Flashcards about the lymphatic system and lymphoid organs and tissues.

What are the three parts of the lymphatic system?

Network of lymphatic vessels (lymphatics), lymph (fluid in vessels), lymph nodes (cleanse lymph)

Which structures provide the structural basis of the immune system?

Spleen, thymus, tonsils, lymph nodes, other lymphoid tissues

What does the lymphatic system return back to the blood?

Interstitial fluid and leaked plasma proteins

Via what structure does the lymphatic system return interstitial fluid and leaked plasma proteins back to blood?

Lymphatic vessels (lymphatics)

Approximately how much interstitial fluid does the lymphatic system circulate per day?

3L

What is interstitial fluid called once it enters lymphatics?

Lymph

Lymphatic vessels offer a one-way system, ensuring lymph flows only in which direction?

Toward the heart

Lymph vessels (lymphatics) include which two types of vessels?

Lymphatic capillaries and larger lymphatic vessels

From which structures are lymphatic capillaries absent?

Bones, teeth, and bone marrow

Lymphatic capillaries are present but limited to locations in which part of the CNS?

Meninges

What do lymphatic capillaries help to drain in the meninges?

Drain interstitial fluid and CSF

What larger molecules and particles can lymphatic capillaries take up that blood capillaries cannot?

Proteins, cell debris, pathogens, and cancer cells

Lymphatic capillaries can act as which type of route?

As a route for pathogens or cancer cells to travel throughout the body

What are the two specialized structures that cause increased permeability in lymphatic capillaries?

Endothelial cells overlap loosely to form one-way minivalves and minivalves are anchored by collagen filaments to matrix

Increases in ECF volume causes minivalves to do what?

Open minivalves even more

Decreases in ECF cause minivalves to do what?

Close minivalves

What are specialized lymph capillaries present in intestinal mucosa called?

Lacteals

What is the function of lacteals?

Absorb digested fat and deliver fatty lymph (chyle) to the blood

Lymph capillaries drain into increasingly larger vessels called what?

Collecting lymphatic vessels

Larger lymphatic vessels consist of what?

Collecting vessels, trunks, and ducts

Compared to veins, larger lymphatic vessels have what type of walls?

Thinner walls, with more internal valves

In comparison to veins, do lymphatic vessels anastomose more or less frequently?

Anastomose more frequently

Collecting vessels in skin travel with which type of veins?

Superficial veins

Deep lymphatic vessels travel with which type of blood vessel?

Arteries

What are formed by the union of largest collecting vessels?

Lymphatic trunks

Name the major lymphatic trunks.

Paired lumbar, paired bronchomediastinal, paired subclavian, paired jugular trunks, and single intestinal trunk

Lymph is delivered from trunks into which two large lymphatic ducts?

Right lymphatic duct and thoracic duct

What areas does the right lymphatic duct drain?

Right upper arm and right side of head and thorax

What areas does the thoracic duct drain?

Rest of the body

In about half of individuals, the thoracic duct starts out as an enlarged sac called what?

Cisterna chyli

Where does each lymphatic duct empty lymph into venous circulation?

At junction of internal jugular and subclavian veins on its own side of body

By what mechanisms is lymph propelled?

Milking action of skeletal muscle, pressure changes in thorax during breathing, valves to prevent backflow, pulsations of nearby arteries, contractions of smooth muscle in walls of lymphatics

Physical activity does what to the flow of lymph?

Increases

What is the term for severe localized edema?

Lymphedema

What causes Lymphedema?

Anything that prevents normal return of lymph to blood

What types of cells are found in Lymphoid tissue?

Lymphocytes, macrophages, dendritic cells, reticular cells

Lymphocytes mature into which two main types of cells?

T cells (T lymphocytes) and B cells (B lymphocytes)

What do macrophages do?

Phagocytize foreign substances and help activate T cells

What do dendritic cells do?

Capture antigens and deliver them to lymph nodes; also help activate T cells

What do reticular cells do?

Produce reticular fibers called stroma in lymphoid organs

What are the main functions of lymphoid tissue?

Houses and provides proliferation sites for lymphocytes and offers surveillance vantage points for lymphocytes and macrophages as they filter through lymph

Lymphoid tissue is largely composed of what type of connective tissue?

Reticular connective tissue

What are the two main types of lymphoid tissues?

Diffuse lymphoid tissue and Lymphoid follicles (nodules)

Describe diffuse lymphoid tissue.

Loose arrangement of lymphoid cells and some reticular fibers

Describe lymphoid follicles (nodules).

Solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers

What do Lymphoid follicles (nodules) contain?

Contain germinal centers of proliferating B cells

Lymphoid follicles are isolated aggregations of what structures primarily?

Peyer’s patches and in appendix

Lymphoid organs are grouped into which two functional categories?

Primary lymphoid organs and secondary lymphoid organs

What are primary lymphoid organs?

Areas where T and B cells mature—red bone marrow and thymus

What are secondary lymphoid organs?

Areas where mature lymphocytes first encounter their antigen and become activated

Name the secondary lymphoid organs.

Lymph nodes, spleen, MALT (mucosa-associated lymphoid tissue) and diffuse lymphoid tissues

What are the principal secondary lymphoid organs of the body?

Lymph nodes

What are the two main functions of lymph nodes?

Cleansing the lymph and immune system activation

What role do lymph nodes play in cleansing the lymph?

Act as lymph “filters”

What role do lymph nodes play in immune system activation?

Offer a place for lymphocytes to become activated and mount an attack against antigens

What is the term for inflamed, swollen, tender lymph nodes that result when nodes are overwhelmed by what they are trying to destroy?

Buboes

The blood-rich organ located in the left side of the abdominal cavity, just below the stomach is called what?

Spleen

What are the functions of the spleen?

Site of lymphocyte proliferation and immune surveillance and response & Cleanses blood of aged blood cells and platelets; macrophages remove debris

Histologically, the spleen consist of consists of which components?

White pulp and red pulp

What occurs at the white pulp of the spleen?

Site where immune function occurs

What occurs at the red pulp?

Site where old blood cells and bloodborne pathogens are destroyed

What is the surgical removal of ruptured spleen called?

Splenectomy

What does MALT stand for?

Mucosa-associated lymphoid tissue

What is mucosa-associated lymphoid tissue (MALT)?

Lymphoid tissues in mucous membranes throughout body

Where are the largest collections of MALT found?

Tonsils, Peyer’s patches, appendix

Name the tonsils.

Palatine tonsils, Lingual tonsil, Pharyngeal tonsil, Tubal tonsils

What is the function of tonsils?

To gather and remove pathogens in food or air

Overlying epithelium invaginates in tonsils, forming what?

Tonsillar crypts

What are clusters of lymphoid follicles in wall of distal portion of small intestine called?

Peyer’s patches

What are the function of Peyer's patches?

Destroy bacteria, preventing them from breaching intestinal wall & Generate “memory” lymphocytes

What is the function of the appendix?

To destroy bacteria, preventing them from breaching intestinal wall and to generate “memory” lymphocytes

Which bilobed lymphoid organ is found in the inferior neck?

Thymus

What is the function of the thymus?

As lymphoid organ where T cells mature

The thymus is broken into lobules that contain which structures?

Cortex and inner medulla

What structures found in the medulla of the thymus is where regulatory T cells develop?

Thymic corpuscles

Regulatory T cells do what?

Help to prevent autoimmunity

Why does the thymus have no follicles?

It lacks B cells

The thymus functions to do what?

Functions strictly in T lymphocyte maturation

What does the blood thymus barrier do?

Keeps immature T lymphocytes isolated from any antigens to prevent premature activation

The stroma of the thymus is made up of what type of cells?

Epithelial cells

Which Lymphoid organs have a capsule?

Lymph nodes and spleen